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paper 2 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what does the nitrogen cycle show

A

how nitrogen is recycled into ecosystems

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2
Q

why do plants and animals require nitrogen

A

in order to produce proteins and nucleic acids

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3
Q

what percentage of the earths atmosphere is nitrogen gas

A

78%

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4
Q

what are the 4 key processes of the nitrogen cycle

A
  • nitrogen fixation
  • ammonification
  • nitrification
  • denitrification
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5
Q

explain the 4 points of nitrogen fixation

A
  • atmospheric nitrogen gas is converted into nitrogen containing compounds
    carried out by nitrogen fixing bacteria
  • the bacteria converts nitrogen into ammonia which forms ammonium ions that can then be used by plants
  • these nitrogen fixing bacterias are found inside the root nodules of leguminous plants (peas,beans,clovers)
  • the bacteria have a symbiotic relationship with the plants
    bacteria provide nitrogen containing compounds
    plants provide organic compounds such as carbohydrates
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6
Q

explain ammonification

A
  • nitrogen compounds in waste products and dead organisms are converted into ammonia by saprobrionts
  • the ammonia forms ammonium ions in the soil
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7
Q

explain nitrification

A
  • ammonium ions in the soil are converted by nitrifying bacteria into nitrates
  • initially nitrifying bacteria convert ammonium ions into nitrites
  • different nitrifying bacteria then convert these nitrites into nitrates
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8
Q

explain denitrification

A
  • denitrifying bacteria use nitrates in the soil during respiration
  • this process produces nitrogen gas, which returns to the atmosphere
  • process occurs in anaerobic conditions
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9
Q

Describe the role of receptors and the nervous system in increasing heart rate during exercise.

A

• Chemoreceptors detect a rise in acidity/fall in pH

• Baroreceptors detect a rise in blood pressure

• Send impulses to medulla;
More impulses to SAN

• Chemoreceptors -
Via the sympathetic NS;

• Baroreceptors -
Via the parasympathetic
NS.

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10
Q

Describe how the mark, release, recapture method could be used to determine the size of a population.

A

Collect a sample, mark and release;

Leave time for sample to disperse before a second collection;

Population = (number in
first sample x number in second sample) / number of marked in second sample.

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11
Q

What is a gene pool?

A

All the alleles in a population

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12
Q

Describe sympatric speciation.

A

Species are not
geographically isolated;

Mutations cause differences;

Reproductive separation/ no gene flow/ gene pools remain separated;

Different alleles are passed on and the frequency of alleles changes;

Disruptive selection;

Eventually, different species can’t interbreed to produce fertile offspring.

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13
Q

What is the difference between interspecific and intraspecific competition?

A

Intraspecific competition:
Occurs between individuals of the same species. E.g. two oak trees competing for sunlight or two male deers competing for a mate.

Interspecific competition:
Occurs between individuals of different species. E.g. a leopard and a lion competing for a common prey.

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14
Q

What is the function of acetylcholinesterase?

A

Acetylcholinesterase catalysed the hydrolysis of ACh into acetate and choline;

Choline is absorbed back into the presynaptic membrane and reacts with acetyl coenzyme A to form ACh;

ACh is then packaged into presynaptic vesicles ready to be used when a new action potential arrives.

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15
Q

Describe what happens if acetylcholinesterase is inhibited.

A

Less acetylcholine broken down;

Acetylcholine attaches to receptors;

More sodium ions enter to reach the threshold for depolarisation/ to trigger an action potential.

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16
Q

Describe the role of calcium ions and ATP in the contraction of a myofibril.

A

Calcium ions diffuse into myofibrils from sarcoplasmic reticulum;

Causing movement of tropomyosin on actin;

This causes exposure of binding sites on actin;
Myosin heads attach to these binding sites;

Hydrolysis of ATP causes myosin heads to bend;

Bending pulls actin molecules and attachment of a new ATP molecule to each myosin head causes them to detach from actin binding sites.

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17
Q

Give two ways in which ATP is a good energy source for cells to use.

A

ANY 2 FROM

Releases small amounts of energy;
Releases energy instantaneously;

Phosphorylates other compounds to make them more reactive;

Can be rapidly resynthesised;

Doesn’t leave cells;

Little energy is lost as heat.

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18
Q

Osmoreceptors are specialised cells that respond to changes in the water potential of the blood.
Where would you find osmoreceptors in the human body?

A

Hypothalamus

19
Q

Describe what happens during photoionisation in the light-
dependent reaction.

A

Chlorophyll absorbs light/ Light excites electrons in chlorophyll;

Electrons are lost/ Chlorophyll becomes positively charged/
Electrons go to the electron transport chain.

20
Q

Explain the advantage of having different coloured pigments in leaves.

A

Absorb different/more wavelengths of light for photosynthesis.

21
Q

Heat stress decreases the
LDR of photosynthesis.
Explain why this leads to a decrease in the light-independent reaction.

A

Less/no ATP;

Less/no reduced NADP.

22
Q

Where is rubisco found in the cell?

A

Stroma

23
Q

Name the features of a calorimeter that enables a valid measurement of the total heat energy released.

A

Thermometer;

Stirrer distributes heat energy;

Insulation reduces loss or gain of heat/reduces conduction;

Water has high specific heat capacity.

24
Q

Name the two products of the LDR that are required for the calvin cycle.

A

ATP;
Reduced NADP.

25
Q

Describe the process of glycolysis.

A

Phosphorylation of glucose using ATP;

Oxidation of triose phosphate to pyruvate;

Net gain of ATP;

NAD reduced.

26
Q

Explain why converting pyruvate to lactate during prolonged exercise allows the continued production of
ATP by anaerobic respiration.

A

Regenerates/Produces
NAD;

Oxidises reduced NAD;

Glycolysis continues.

27
Q

Describe the advantage of the Bohr effect during intense exercise.

A

Increases dissociation of oxygen;

For aerobic respiration at the tissues/muscles;

Anaerobic respiration delayed at the tissues/ muscles;

Less lactate at the tissues/ muscles.

28
Q

Describe the role of saprobionts in the nitrogen cycle.

A

They use enzymes to decompose proteins/DNA/ RNA/urea;

Producing/Releasing ammonia/ammonium ions.

29
Q

Describe how alterations to tumour suppressor genes can lead to the
development of tumours.

A

Increased methylation of tumour suppressor genes;

Mutation in tumour suppressor genes;

Tumour suppressor genes aren’t
transcribed/ expressed;

Amino acid sequence/ primary structure altered;

Results in rapid/ uncontrollable cell division.

30
Q

Define epigenetics.

A

Heritable changes in gene function;
Without changes to the base sequences of DNA.

31
Q

Explain how increased methylation could lead to cancer.

A

Methyl groups added to a tumour suppressor gene;

The transcription of tumour suppressor genes is inhibited;

Leading to uncontrolled cell division.

32
Q

How are benign tumours different to malignant tumours?

A

Benign tumours - Cells cannot spread to other parts of the body and cannot invade neighbouring tissues.

Malignant tumours - Cells spread to other parts of the body and invade neighbouring tissues.

33
Q

Suggest how transcription factors could reprogramme cells to form iPS cells.

A

Transcription factors attach to gene/DNA/promoter region;

Stimulate/inhibit transcription/RNA polymerase.

34
Q

Name two techniques scientists could used to analyse viral DNA to determine how closely related the viruses are.

A

ANY 2 FROM

Polymerase chain reaction;

DNA fingerprinting;

Gel electrophoresis;

Genome sequencing.

35
Q

Explain how determining the genome of a virus allows scientist to develop a vaccine.

A

The scientist could identify proteins;

The scientist could identify the proteome;

They could then identify potential antigens to use in the vaccine.

36
Q

Describe how B
lymphocytes would respond to a vaccine.

A

B cells bind to
complementary receptors/ antigens;

B cell forms an antigen-antibody complex;

B cell clones/divides by mitosis;

Plasma cells release antibodies;

B cells produce memory cells.

37
Q

Define genome.

A

All the DNA in a cell

38
Q

What is a DNA probe?

A

Short single strand of DNA;

Bases complementary with DNA/allele/gene.

39
Q

Explain how drug treatments can reverse epigenetic changes that cause cancer.

A
  • drugs could increase methylation of oncogenes.
  • drugs could decrease methylation of tumour suppressor genes.
  • Increased methylation of DNA inhibits transcription /gene expression.
  • Decreased acetylation of histones inhibits transcription /gene empression.
40
Q

Describe how DNA from saliva can be screened.

A

Use PCR to amplify DNA sample;

Cut DNA using restriction endonuclease;

Separate DNA fragments using electrophoresis;

Add labelled DNA probes and bind by DNA hybridisation;

Identify genes/ mutations by fluorescent dyes/radioactivity/x-ray/ photographic film/UV light.

41
Q

Explain why impulses travel faster along myelinated axons compared to non-myelinated axons.

A

• myelination provides electrical
insulation.

• myelinated axons have saltatory conduction/ depolarisation at nodes of Ranvier.

• non-myelinated axons: depolarisation occurs along the whole rength of
the axon

42
Q

Describe the light-independent reaction/ calvin cycle of
photosynthesis.

A

• CO2 reacts with RuBP
• produces 2 GP using the enzyme rubisco
• GP is reduced to triose phosphate using reduced NADP/NADPH* and energy from ATP
• Triose phosphare conversed to RuBP and glucose/named organic substance

43
Q

Name and compare the two types of summation.

A

Spatial
• Multiple neuron’s collectively trigger an action Potential by combining the neurotransmitters they release to exceed the threshold value
• simultaneous impulses
• large amounts of ACH released into synaptic cleft
• multiple synaptic knobs

TEMPORAL
• quick succession
• large amount of ach
• 1 synaptic knob

44
Q

What are the conditions for the Hardy-
Weinberg principle?

A

→ organisms are diproid.
→ organisms produce by sexual
reproduction only.
→ mating is random.
→ the population is large.
→ there is no overlap between
generations.
→ there is no mutation.
→ there is no immigration /emigration.
→ there is no selection (natural
or artificial).
→ allele frequencies are equal
in both sexes.

Biology (6 decks)

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